This invention relates generally to wind turbines, and more particularly to methods and apparatus for measuring wind turbine blade deflection.
Wind power is quickly becoming a growing energy source around the world. As such, wind turbines are increasing in size and capacity. Specifically, to increase energy output, rotor blade length is increased while rotor blade weight is decreased. Due to this increase in size and decrease in weight, the rotor blades are subject to greater deflection forces. However, due to the greater deflection forces, the risk of one of the rotor blades striking the wind turbine tower is increased. In addition, rotor blade deflection produces fatigue in the rotor blades and other wind turbine components. To minimize fatigue, many modern wind turbines use rotor blade pitch control strategies that require measuring the deflection of one or more rotor blades.
Known wind turbines include sensors for detecting rotor blade deflection. These sensors are typically mounted on the rotor blades. Accordingly, communication signals and/or power cables must be provided across a pitch axis of the rotor blades. As such, known wind turbines utilize slip ring, twisted-wire, or radio-frequency methods to bring the communication or power cables from the rotor blade to the rotor hub. However, these techniques increase assembly and maintenance time, and increase the complexity of obtaining data relating to the rotor blade deflection. Accordingly, measurement techniques of the kind presently in use have not previously provided blade deflection measurements in a cost effective and reliable manner.